Tank for energy recovery

ABSTRACT

A tank for waste water partially or fully buried in the ground or immersed in water includes a wall made of a high thermal conductivity material, which in turn has a pair of walls forming a cavity creating a circuit of a convective fluid for heat exchange with both the waste water contained inside the tank and with the ground and/or groundwater external to the tank.

This patent is related to the energy recovery facilities within the home environment, and in particular concerns a new tank for waste water integrated with an energy recovery plant for the use of one or more heating/cooling pumps in the civil, service in general, industrial, and agricultural sectors.

Civil, industrial, commercial, and agricultural units equipped with heating and cooling systems based on heat pumps and coolers are already known.

Geothermal energy systems are also known and used to power residential units and in particular to operate heating and/or cooling heat pump based systems, but also to produce hot water for domestic use.

The advantages resulting from the use of geothermal systems are numerous and varied. First and foremost is its economic advantage, resulting from the exploitation of “free” thermal energy supplied by the ground or a body of water, which ensure relatively constant temperature values regardless of ambient temperatures.

In addition, geothermal systems lead to other ecological and environmental benefits as they reduce polluting emissions and environmental impact and lead to reductions in operating costs and electricity consumption, particularly in the summer for air conditioning.

Geothermal plants of the known type comprise at least one geothermal heat pump, suited to be installed inside the residential unit or building in general, which has the function of transferring heat between the inside of the house and the ground or the water, reversing the cycle between the phases of heating and cooling, using a convective fluid circulating in an exchange system to capture heat.

In fact, geothermal installations include at least one heat collection system which in turn consists of a piping system, generally polyethylene, distributed under ground level in contact with the ground or water, and in which the exchange fluid circulates. These pipes act as heat exchangers, exploiting the thermal energy stored in the ground or in a body of water.

These pipes, or vertical geothermal loops, can be arranged to form substantially vertical coils, buried at great depths in the ground, in order to exploit the high thermal capacity of the soil mass that remains at a practically constant temperature throughout the year, independent of the weather outside.

Alternatively, geothermal systems that use horizontal loops or collectors, arranged like a coil 1-2 meters deep, but involving greater surfaces in order to have a large surface area for exchange are known.

Geothermal installations generally also comprise a system of heat accumulation and distribution comprising in general a hot water storage tank, suited to store heat to then be distributed to the rest of the building, for heating or for domestic use, when it is required. Generally, this storage tank is connected to both the geothermal system's collection circuit and any other heat generating systems, such as solar thermal systems or condensing boilers.

The heat pumps work by exchanging heat with a natural source, such as the ground, bodies of water, or air, absorbing thermal energy to use it for heating.

In contrast, by reversing the cycle of the heat pump, the ground or underground body of water are used to dissipate the heat taken from the environment to be cooled.

However, geothermal installations have some drawbacks, including the high cost of installation resulting from deep drilling.

These costs are particularly high in the case of installations of vertical geothermal loops.

On the other hand, the installation of horizontal geothermal loops requires excavations that are not as deep, and thus at a lower cost, but of larger surfaces, often not available, especially in the case of existing buildings.

Concrete tanks for the collection of waste water from civil or residential users are known. This water is even discharged at temperatures above 20-30° C., but the heat contained in it is not exploited but rather dispersed into the environment.

To overcome all the above drawbacks, a new type of tank for the collection of waste liquids from civil, industrial, commercial and agricultural buildings or plants combined with an energy recovery plant for the use of one or more heating/cooling pumps has been designed and developed.

The main purpose of the present invention is to utilize the heat present in the waste water from, for example, civil, industrial, agricultural, commercial or residential users, to produce and transfer thermal energy useable for domestic, industrial, or commercial purposes.

Another purpose of the present invention is to also use the thermal energy stored in the ground and/or in groundwater, together with the thermal energy taken from domestic waste water.

A further purpose of the present invention is to combine the functions of separation of grease/scum or sludge in a single tank in which a convective fluid circulates that is suited to exchange heat with both the waste water and the ground/groundwater in which the tank is wholly or partially buried/immersed.

Yet another purpose of the present invention is to be used as an alternative to current geothermal installations, used in any sector, which involve the drawbacks described above.

Another purpose of the present invention is that it can also be installed in limited spaces, that is, in the case when the available surfaces are limited.

A further purpose is to limit installation costs, since deep excavations are not necessary.

These and other purposes, direct and complementary, are achieved by the new tank for waste water combined with an energy recovery plant for the use of one or more heating/cooling pumps for the civil, domestic, residential, industrial, agricultural, and commercial sectors.

This is a new tank or reservoir preferably with a cylindrical shape, arranged preferably vertically, made of a material with high thermal conductivity and high resistance to corrosive agents and oxidants in general. In the preferred embodiment, this tank is made of stainless steel, such as AISI 304, constructed with TIG welding, but any other material with good conductivity can be used as well, such as copper, aluminium, polyethylene, resins, etc.

The new tank can also be used as a conventional collection tank for waste fluids from residential or civil structures suited to collect waste water from kitchens, showers, sinks, bidets, and equipment such as dishwashers, washing machines and the like.

The tank in question comprises at least its side walls and preferably also its bottom, constructed of a double wall that creates a cavity or space in which the exchange fluid circulates, suited to exchange heat with the contents of the tank and with its external side, that is, with the ground/groundwater, which is at a constant temperature of about 12-14° C.

The new tank or reservoir includes couplings for the connection to the heat pump, couplings for the connection to the circuit of soapy waste water from domestic or civil uses in general, and couplings for the connection to the sewer system.

The new tank or reservoir also preferably includes one or more means or lifting points for its handling and positioning by means of a jib crane.

The new tank or reservoir also includes a lid that ensures its safety for pedestrian traffic.

For example, the new tank or reservoir is particularly suited to be buried at a depth such as to ensure the smooth operation of the grease separator system for a residential unit connected to the sewer and the disposal of the resulting grease condensate. It is particularly appropriate that the aforementioned lid, which is the upper side of the tank, is at least 70 cm below the ground level.

Thus the new geothermal tank is suited to be installed underground and connected to the heating/cooling pump of a residential unit and serves as a geothermal condenser transferring the cooling or thermal power produced by the heating/cooling pump by means of the exchange fluid circulating in the cavity of the walls.

Said heating/cooling pump has in fact a refrigeration cycle operating for the production of thermal energy for heating or cooling environments or for the production of domestic hot water.

Said cooling fluid is preferably a certified glycol based solution not harmful to the environment.

The new tank thus operates as a condensation circuit at the mean temperature of the ground and any groundwater present in the area where the new tank is partially or fully buried or immersed. This temperature ensures a COP (Coefficient of Performance) of about 6 for heating and an EER (Energy Efficiency Ratio) of about 4.5 for cooling.

This optimal operating condition of the heat pump is complemented by the reuse of the heat recovered by a static recovery system installed inside the tank as described and claimed below, where the recovery system itself stores the thermal energy transferred from the waste water flowing into the tank to be treated before being discharged into the public sewage. This recovered energy further increases the energy performance of the heat pump.

The new tank can be conveniently connected to class A and B low energy systems, with variable heat loads such as heating, cooling and domestic hot water systems. Therefore the new tank also operates as an energy accumulator for subsequent reuse of the condensation energy of the cooling system.

In an example of operation, during the warm season, when a radiant or fan convector system is used inside the premises, cooling energy is produced for the evaporator inside the premises transferring the condensation thermal energy into the new tank, that is, the heat extracted from the environment.

When the cooling system reverses the cycle, for example to produce domestic hot water, it works with the high temperatures of the condensation fluid and therefore with high COPs and consequently stores the cooling power produced in the tank. At the end of the domestic hot water production cycle, returning to the production of cooling energy, given that the working temperatures are low, the EER will be high.

The circuit of the heat exchange fluid is substantially created in the aforementioned hollow space of the tank and is preferably made of AISI 304 stainless steel with TIG welding. The circuit is composed of at least one geothermal injector and a specific positioning of the delivery outlet and return inlet. The circuit is preferably loaded with a glycol based fluid.

The tank is suitably connected to the heating/cooling pump with chased pipes and uses the regulation, safety and control accessories required by current legislation installed in the pump itself or along the connection pipes.

The treatment circuit is integrated with the new tank and is preferably made of AISI 304 stainless steel with TIG welding and comprises at least one baffle for energy recovery, in turn formed by one or more internally hollow walls in which the thermoconvective fluid circulates, at least one divider, and connections for the waste water inlet and the waste water outlet.

The characteristics of the new tank will be better clarified by the following description with reference to the drawings, attached by way of non-limiting example.

FIGS. 1a, 1b and 1c respectively show a top view and two vertical sections of a new tank (1) illustrating the application as a fat and grease separator tank.

FIGS. 1b and 1c respectively show the circuit (Wa) of waste water (A) coming from a residential unit in general and the circuit (Wb) of the exchange fluid (B).

FIGS. 2a, 2b and 2c respectively show a top view and two vertical sections of the new tank (1) in a possible preferred embodiment.

FIG. 3 shows the connection of the new tank (1) to the waste water pipe (S) of the water from a residential unit to the supply pipe (F1) and to the sewer system (F).

FIG. 4 shows the connection of the new tank (1) to a heating/cooling pump (C).

This is a tank (1) for the separation of fat and grease in waste water (A) coming from a residential unit or building in general and is suited to be partially or fully buried, thus being in contact with the ground and/or with groundwater or an underground body of water in general.

The new tank (1) for the separation of fat and grease is made of a high thermal conductivity material, preferably stainless steel, and comprises a wall (11) preferably cylindrical or prismatic and preferably installed in a vertical position, a bottom (12), preferably convex and a lid (13) to close it.

At least the wall (11) and preferably also the bottom (12) are in turn made up of a double wall in highly conductive material or steel, an outer wall (21) and an inner wall (22), that create a hollow cavity (23, 24). In the preferred embodiment, this hollow cavity (23) created in the wall (11) communicates with the cavity (24) created in the bottom (12).

The interior (14) of the tank (1) in turn communicates via an inlet and outlet (S1, S2) respectively with a waste water pipe (S) for the waste water coming from a housing unit in general and with an outlet pipe (F1) that leads to the sewer system (F).

Inside (14) the tank (1) there are one or more baffles (15, 16) and in particular at least one baffle is a T-shape, formed by a first baffle (15) which divides the interior (14) into two parts (141, 142) communicating with each other and a further baffle (16) transverse to the first baffle (15).

Said T-shaped baffle (15, 16) is spaced from the bottom (12) of the tank (1) so as to create a passage (A1) for the flow (Wa) of the waste water (A) between the inlet (S1) and the outlet (S2), which are in turn located near the top of the tank (1).

On the bottom (12) of the tank (1) there is at least one divider (17) for the separation of fats and grease, which rises from the bottom (12) and has a height higher than the passage (A1) for the waste water (A), such as to form a barrier for fats and impurities contained in the waste water (A).

The flow (Wa) of the waste water (A) inside the tank (1), between the inlet (S1) and the outlet (S2), is shown schematically in FIGS. 1b and 2 b.

A preferably glycol based heat exchange fluid (B) circulates inside the cavity (23, 24) in the wall (11) and in the bottom (12) of the tank (1).

In particular, within the cavity (23, 24) a circuit (Wb) is created for the exchange fluid (B), connected to a heat pump (C).

Said exchange fluid (B) is inserted into and removed from the tank (1) via multiple delivery and return connections (B1, B2, B3, B4).

In the preferred embodiment, there are two circuits, one for the hot season and one for the cold season, and therefore at least one pair of delivery/return connections (B1, B2) for operation in the hot season and at least one pair of delivery/return connections (B3, B4) for operation in the cold season.

Therefore, said exchange fluid (B) circulates within said cavities (23, 24) in the wall (11) and in the bottom (12) of the tank (1), and is therefore able to exchange heat with both the waste water (A) contained inside (14) the tank (1) and the outside (E) of the tank (1), that is, with the ground and/or groundwater.

Said tank (1) is appropriately sized as a function of the number of users to be served, and also in order to optimize the efficiency of the heat exchange with both the waste water (A) and with the external ground/groundwater (E), and has, for example, a diameter between 80 and 100 cm and a height preferably between 160 and 200 cm.

To improve the circulation of the exchange fluid inside said cavity (23) in the wall (11) of the tank (1) between the inner wall (21) and the outer wall (22) there is at least one helical baffle (19) installed suited to create a forced spiral path (Wb) inside said cavity (23), so as to convey the heat exchange fluid (B) across most of the surface.

For this purpose, the new tank (1) may include one or more temperature probes placed in said cavities (23, 24, 25) or in other parts of the tank (1).

To increase the heat exchange surface with the interior (14) of the tank (1), said baffles (15, 16) are also made of material with high thermal conductivity, preferably stainless steel, formed by a double wall creating one or more cavities (25) communicating with said cavities (23, 24) of the wall (11) and the bottom (12) of the tank. In this way the glycol based fluid (B) also circulates in said cavity (25) in the baffles (15, 16).

To increase the heat exchange surface with the outside (E) of the tank (1), a plurality of fins (18) are mounted, preferably welded, and arranged, for example, radially and evenly distributed on the outside of said wall (11) of the tank (1). The exchange surface between the glycol based fluid (B) and the outside (E) is thus the sum of the surfaces of all the fins (18), the outer surface of the wall (11), and the outer surface of the bottom (12).

Said circuit (Wb) of the glycol based fluid (B) communicates with at least one heat pump (C), by means of suitable electromechanical devices, valves, sensors, and the like which are needed for the proper management of the system.

These specifications are sufficient for the expert person to make and use the invention, as a result, in the practical application there may be variations without prejudice to the substance of the innovative concept.

Therefore, with reference to the preceding description and the attached diagrams the following claims are made. 

The invention claimed is:
 1. A tank (1) for waste water (A) coming from civil, industrial, commercial, and agricultural units, adapted to be partially or fully buried, being in contact with a ground and/or groundwater or an underground body of water, comprising: a wall (11); a bottom (12); and a lid (13) for closure, wherein at least said wall (11) is made of a thermally conductive material, and wherein said wall (11) comprises a pair of walls (21, 22) forming a cavity (23), in which a circuit (Wb) is created for a convective exchange fluid (B) for heat exchange with both the waste water (A) contained inside (14) the tank (1) and with the ground and/ or water outside (E) the tank (1).
 2. The tank (1), according to claim 1, wherein said circuit (Wb) for said exchange fluid (B) is connected to a heating/cooling pump (C).
 3. The tank (1), according to claim 1, wherein said bottom (12) is made of a thermally conductive material and includes a double wall creating a cavity (24) communicating with said cavity (23) in the wall (11).
 4. The tank (1), according to claim 1, further comprising at least one baffle and one or more dividers (15, 16, 17) mounted on an inside (14) of the tank (1) for separation of waste products and creating a circuit (Wa) for waste water (A) circulation between an inlet (S1) and an outlet (S1, S2), respectively connected to an incoming waste water pipe (S) and to an outlet pipe (F1) that leads to a public sewer network (F), wherein said baffle is T-shaped (15, 16) and is formed by a first baffle (15)M, which divides an interior (14) into two parts (141, 142) communicating with each other, and a second baffle (16) transverse to said first baffle (15), said T-shaped baffle (15, 16) being spaced from the bottom (12) of the tank (1) so as to create a passage (Al) for flow (Wa) of waste water (A) between said inlet (S1) and outlet (S2), which are placed near a top of the tank (1), and wherein, on the bottom (12) of said tank (1), there is at least one divider (17).
 5. The tank (1), according to claim 4, wherein said at least one baffle (15, 16) comprises a double wall, which creates one or more cavities (25) communicating with said cavities (23, 24) of the wall (11) and the bottom (12) of the tank, such that said exchange fluid (B) also circulates in said cavity (25) of said baffles (15, 16), increasing an exchange surface with the waste water (A) inside (14) the tank (1).
 6. The tank (1), according to claim 1, wherein at least one helical baffle (19) is mounted inside said cavity (23) of said wall (11) of the tank (1), the at least one helical baffle creating a substantially spiral forced path (Wb) inside said cavity (23) of said wall (11).
 7. The tank (1), according to claim 6, further comprising a plurality of fins (18) which are configured to increase an exchange surface between the convective fluid (B) and the outside (E) of the tank (1), the plurality of fins being mounted at least outside said wall (11) of the tank (1).
 8. The tank (1), according to claim 6, wherein said heat exchange fluid is a glycol based fluid (B) and that said wall (11), said bottom (12), and said baffles (15, 16) are made of stainless steel.
 9. The tank (1), according to claim 2, wherein said circuit (Wb) of the exchange fluid (B) is connected to said heating/cooling pump (C) in two circuits, of which one is for hot season and one for cold season, and wherein said tank (V) comprises at least one pair of exchange fluid (B) delivery/return connections (B1, B2) for operation in the hot season and at least one pair of exchange fluid (B) delivery/return connections (B3, B4) for operation in the cold season.
 10. The tank (1), according to claim 1, wherein the tank is cylindrical or prismatic, with a diameter between 80 and 100 cm and a height between 160 and 200 cm. 